Three element photographic objective



SEARCH RO Sept. 25, 1956 a. LANGE THREE ELEMENT PHOTOGRAPHIC OBJECTIVE Filed Sept. 16. 1954 Fig.1

W m m.

Fig.2-

United States Patent THREE ELEMENT PHOTOGRAPHIC OBJECTIVE Giinther Lange, Konigsbronn, Wurttemberg, Germany,

assignor to Carl Zeiss, Heidenheim (Brenz), Wurttemberg, Germany Application September 16, 1954, Serial No. 456,431

Claims priority, application Germany September 23, 1953 4 Claims. (CI. 88-57) The present invention concerns photographic objectives, which consist of three elements separated from one another by air spaces, namely of a collective meniscusshaped front element, of a dispersive biconcave middle lens and of a collective rear element, which consists of two cemented together lenses of opposite refractive power, whereby the cement surface of the rear element turns its convex side towards the middle lens and has a radius which is longer than 30% but shorter than 50% of the objective focal length.

In order to attain in such objectives a balanced coma correction, the dispersive biconcave middle lens in accordance with the invention is bent in such manner, that the radius of the surface facing the front element is longer in amount than 95% but shorter than 150% of the objective focal length, and the first air space is selected smaller than the second, and the over-all length is selected within the limits 020-1 and 050-1, and if further the curvatures of the glass-air surfaces are adjusted to one another, that the sum of the refractive powersof the two outer surfaces lies within the limits 2.8/1 and 42/), and that the sum of the refractive powers of the two surfaces of the two collective outer elements turned towards the middle lens lies within the limits 0.6/f and 0.15/ f, and that the sum of the refractive powers of the two concave surfaces of the middle lens lies within the limits 3.2/ f and 2.6/f.

The following numerical values and the accompanying illustrations or Figures 1 to 3 refer to three execution examples in accordance with the invention. These obby r1 to r'z=the radii of the refracting surfaces by d1 to d4=the axial lens thicknesses by 11, l2=the axial distances between the lens elemen Nn=the refractive index for the D line of the lens material V=the dispersion ratio or Abbe number of the lens material f=the objective focal length: 1

AN/r=the refractive power of the surface having the radius r.

Example I Thlcknesses Lenses Radii and N V AN/r Distances r1=+0. 331104 +2. 17415 Ll dx=0. 05142 1. 72000 50. 3

l1=0. 03955 r3= --1. 10928 -0. 58444 Ln di=0. 05471 1. 64831 33. 8

la=0. 05933 =--3. 17162 0. 16765 Lu: da=0. 01318 1. 53172 48. 9

rs=+0. 350781 +0. 53675 Llv d4=0. 06592 1.72000 50. 3

Example [I Thieknesses Lenses Radll and N V AN/r Distances fl=+0- 335931 +2. 14330 L! d1=0. 05220 1.72000 50. 3

li=0. 05352 rs= 1. 10918 -0. 60648 Lu (12 0- 04891 1. 67270 32. 2

[i=0 06684 rs= m 0. 00000 Lm da=0. 01318 1. 59551 39. 2

rs=+0. 335931 +0. 44203 LIV d4=0. 07910 1. 74400 44. 7

Example Ill Thicknesses Lenses Radii and N n V AN/r Distances n=+0. 32776 +2. 19673 Lt dr=0. 05200 1. 72000 50. 3

l1=0. 05000 r3= 1. 12187 0. 59436 Ln dz=0. 04267 1. 66680 33.1

lz=0. 05960 4. 15613 0. 12586 L111 da=0. 01333 1. 52310 50. 9

r=+0. 35476 +0. 55502 LIV |i|=0. 09200 1. 72000 50. 3

I claim:

1. Photographic objective consisting of three elements separated from one another by air spaces, namely of a collective meniscus-shaped front element, of a dispersive biconcave middle lens and of a collective rear element, said rear element consisting of two cemented together lenses of opposite refractive power, the cement surface of the said rear element turning its convex side towards the middle lens and having a radius longer than 30% but shorter than 50% of the objective focal length, the radius of the surface of the said middle lens turned towards the said front element being greater in amount than but smaller in amount than of the objective focal length, and the first air space being smaller than the second, the over-all length being more than 20%, but less than 50% of the focal length, and the sum of the refractive powers of the two outer surfaces lying within the limits 2.8/f and 4.2/ f, and the sum of the refractive powers of the two surfaces of the two collective outer elements turned 2. Photographic objective consisting of three elements separated from one another by air spaces, namely of a collective meniscus-shaped front element, of a dispersive biconcave middle lens and of a collective rear element,

'said rear element consisting of two cemented together lenses of opposite refractive power, the cement surface of the said rear element turning its convex side towards the middle lens and having a radius longer than 30% but shorter than 50% of the objective focal length, the radius of the surface of the said middle lens turned towards the said front element being greater in amount than 95% but smaller in amount than 150% of the objective focal length, and the first air space being smaller than the second, the over-all length being more than 20%, but less than 50% of the focal length, and the sum of the refractive powers of the two outer surfaces lying within the limits 2.8/f and 42/1, and the sum of the refractive powers of the two surfaces of the two collective outer elements turned towards the middle lens lying within the limits 0.60/ f and -0.l5/f, and the sum of the refractive powers of the two concave surfaces of the middle lens lying within the limits 3.2/f and 2.6/f, the refractive powers (AN/r) each differing by at inost iOJS/f and the lens thicknesses (d) and the air distances (I) each by at most $0.025 f from the values to be taken from the following numerical example:

Thicknesses Ni. V

AN/r and Distances Lenses Radii tit=0. 06592-1 (n to r1) =the radii of the refracting lens surfaces (d1 to d4) =the axial lens thicknesses (Ir, [2) =the axial distances between the lens elements 1 Nn=the refractive index of the lens materials 3. Photographic objective consisting of three elements separated from one another by air spaces, namely of a collective meniscus-shaped front element, of a dispersive biconcave middle lens and of a collective rear element, said rear element consisting of two cemented together lenses of opposite refractive power, the cement surface of the said rear element turning its convex side towards the middlev lens and having a radius longer than 30% but shorter than 50% of the objective focal length, the radius of the surface of the said middle lens turned towards the said front element being greater in amount than 95% but smaller in amount than 150% of the objective focal length, and the first air space being smaller than the second, the overall lcngth being more than 20%, but less than 50% of the focal length, and the sum of the refractive powers of the two outer surfaces lying within the limits 2.8/f and 4.2/ and the sum of the refractive powers of the two surfaces of the two collective outer elements turned towards the middle lens lying within the limits 0.60/f and 0.15/ and the sum of the refractive powers of the two concave surfaces of the middle lens lying within the limits -3.2/f and 2.6/f,- the refractive powers 4 (AN/r) each differ by at most 0.15/f and the lens thicknesses (d) and the air distance (I) each by at most :0.025- I from the values to be taken from the following numerical example:

Lenses Radll Thiclmssses N, V AN/r and Distances n =+0. 335931- f +2. 14330 LI d =0. 05220-1 1. 72000 50. 3

l1=0. 05352-f =1.10918-/ 0. 60648 Ln tia=0. 04891-f 1. 67270 32. 2

l2=0. 06684-1 r;: w 0. 00000/! Lm da=0. 0l318-f 1. 59551 39. 2

rs=+0. 335931-1' +0. 44203/1' I LIV tit=0. 079104 1. 74400 44. 7

(n to n) =the radii of the refracting lens surfaces (d1 to d4) =the axial lens thicknesses ([1, I2) =the axial distances between the lens elements N n=the refractive index of the lens materials V= dispersion ratio or Abbe number of the lens material 1: the objective focal length 1 AN r: the refractive power of the surface having a radius (r) said front element being greater in amount than but smaller in amount than of the objective focal length, and the first air space being smaller than the second, the over-all length being more than 20%, but less than 50% of the focal length, and the sum of the refractive powers of the two outer surfaces lying within the limits 2.8/f and 4.2/f, and the sum of the refractive powers of the two surfaces of the two collective outer elements turned towards the middle lens lying within the limits 0.60/f and -0.15/f, and the sum of the refractive powers of the two concave surfaces of the middle lens lying within the limits 3.2/ and 2.6/f, the refractive powers AN/ r) each differ by at most $0.15 f and the lens thicknesses (d) and the air distances (1) each by at most i0.025f from the values to be taken from the following numerical example:

(r1 to n) =the radii of the refracting lens surfaces (d1 to d4) =the axial lens thicknesses (l1, l2) =the axial distances between the lens elements Nn=the refractive index of the lens materials V= dispersion ratio or Abbe number of the lens material f= the objective focal length =1 AN/r=the refractive power of the surface having a 1,558,073 Bielicke Oct. 20, 1925 radius (r) 1,849,681 Merte et a1 Mar. 15, 1932 2,084,714 Tronnier June 22, 1937 References Clted 1n the file of th1s patent FOREIGN PATENTS UNITED STATES PATENTS 583,984 Great Britain Jan. 3, 1947 721,240 ph Feb-24, 1903 714,565 Great Britain Sept. 1, 1954 

